Various publications are cited throughout the application. Each of these publications are incorporated by reference into the application to more fully describe the invention.
It is well documented in animal models that cells, after neoplastic transformation in vivo, are changed biochemically and morphologically. In sufficient numbers, such transformed neoplastic cells are capable of inducing protective immunity against tumor development in syngeneic animals which are subsequently inoculated with viable cancer cells. This protective immunity was determined to be due to certain new cell components, called tumor specific transplantation antigens that were expressed by the neoplastic cells.
Expression of similar unique components by malignant cells is the fundamental hypothesis upon which tumor immunology is based. Substantial and convincing evidence now exist that clearly supports the concept that neoplastic transformation is associated with antigenic changes on the mammalian cell surfaces (Reisfeld R A and Cheresh D A: Ad Immunol 40:323-377,1987). To define a large group of cell surface antigens that appear to have, at least, increased expression on human tumor cells a variety of serologic strategies have been utilized (Old L J: Cancer Res 41:361-375,1981; Rosenberg S A, (ed.) Serologic Analysis of Human Cancer Antigens. Academic Press, New York. 1980.),. The advent of hybridoma technology has provided highly specific and reproducible reagents for the study of cell surface antigens on human tumors.
The majority of antigens defined by monoclonal antibodies have proven to be glycoproteins (Liao S K, et al. Int J Cancer 30:573-580,1982., Loop S M, et al. Int J. Cancer 27:775-781,1981., Mitchell K F, et al. Proc Natl Acad Sci, USA, 77:7287-7291,1980., Woodbury R G, et al. Proc Natl Acad Sci, USA. 77:2183-2187,1980). Utilizing murine monoclonal antibodies, a number of other melanoma associated antigens have been described (Mitchell K F, et al. Proc. Natl. Acad. Sci., USA, 77:7287-7291,1980; Woodbury R G, et al. Proc. Natl. Acad. Sci., USA. 77:2183-2187,1980; Dippold W G, et al. Proc. Natl. Acad. Sci., USA 77:6114-6118,1980; Cheresh D A, et al. Proc. Natl. Acad. Sci,, USA. 81:5767-5771,1984; Pukel C S, et al. J. Exp. Med., 155:1133-1147,1982; Yeh M Y, et al. Int. J. Cancer 29:269-275,1982). The majority of these antigens have been defined by cross reactivity in xenogeneic systems. It is apparent that murine monoclonal antibodies will most often define only strong species-specific antigens. Thus, subtle alterations in the tumor cell surface which most probably are critical to the unregulated growth of the malignant cell, may not be detected.
No evidence exists that antigens defined by murine monoclonal antibodies are immunogenic in the human host. Therefore, tumor associated antigens that are recognized as foreign and are immunogenic in man are of particular importance and may be critical both in the control of the cancer and as potential as diagnostic and or therapeutic reagents.
Tumor associated antigens that have been defined by autologous and allogeneic antibodies in human neoplasms can vary widely in their distributions. Some tumor associated antigens are expressed only by an individual tumor cell line or tumor. Others are shared by histologically similar tumors and still others by a variety of histologically distinct cancers including organs from which the tumor arose from and fetal tissues. Those antigens that are expressed only by an individual tumor are of limited importance for immunodiagnosis and treatment of cancer since tumor cell lines generally cannot be established from every tumor and cannot be applied to another patient. In contrast, tumor antigens that are shared by different tumors of the same histologic type or by histologically dissimilar tumors have potential application for immunodiagnosis, immunoprognosis and treatment of different patients with various types of malignancies.
There are well-documented instances which suggest that immunity against growing neoplasm in humans can be enhanced by active immunization with antigen-bearing tumor cells. The purpose of such active specific immunotherapy is to enhance the level of anti-tumor immunity beyond that which is naturally induced by the growing neoplasm. It is believed that a growing neoplasm does not induce a maximum immune response in the host to the tumor associated antigens it contains. Most immunotherapy attempts thus far have involved vaccines prepared from whole tumor cells, because progress has been slow in the isolation and purification of human tumor associated antigens. The possibility that living autologous tumor cells could result in tumor growth at the inoculation site has inhibited the use of such vaccines in man. However, tumor cells that express high levels of shared common tumor-associated antigens can be used to immunize different patients (Morton, D. L. et al, In Terry, W. D., Rosenberg, S. A. (eds): Immunotherapy of Human Cancer. New York, Elsevier North Holland, pp 245-249 (1982); Livingston P. O., et al., Int. J. Cancer 31:567 (1983)). The advantage of using such an allogeneic vaccine is two-fold: (1) an immune response induced against the foreign HLA transplantation antigens on the allogeneic vaccinated tumor cells would cause their rejection; (2) this immunization should induce a strong immune response against the shared common cross-reacting tumor-associated antigens to which the human leukocyte antigens (HLA) might serve as a helper function.
Approximately 40% of melanoma sera have been shown to contain antibodies to an antigen that was present in the partially purified spent culture medium of a melanoma cell line, (Gupta et al. JNCI 63:347-356 (1979)). The antigen was subsequently partially purified from the spent culture media of a melanoma cell line. Under nondissociating conditions, a gradient polyacrylamide gel electrophoresis (PAGE) analysis revealed that the antigen was a complex of about 450 kD which, by SDS (PAGE) analysis, under dissociating conditions, resolved into at least 5 bands that were stainable by Coomassie blue. One or two of these bands in the 60 to 70 kD range reacted with the antibody present in an allogeneic serum. This antigen, because of its cross reactivity with fetal tissues, was designated fetal antigen (FA) (Gupta R K and Morton D L: JNCI:70;993-1003 (1983)). Prevalence of antibody to the antigen in cancer and non-cancer sera was frequent (56-88%). The antigen appeared to be widely expressed on melanoma, carcinoma, and sarcomas as well as on human fetal liver and brain but only infrequently on normal tissues obtained from non-cancer patients. Immunochemical characterization of the partially purified antigen preparation suggested the antigen to be a glycoprotein. The epitope recognized by human antisera was heat stabile and the immunoreactive part of the molecule was the carbohydrate portion of the antigenic complex molecule.
Obviously, the identification of additional tumor associated antigens is extremely important for diagnosis and treatment of cancers, particularly where the antigen is present on a large percentage of tumor cells but not normal cells. The present invention satisfies this need by providing a tumor-associated antigen. This antigen while discovered in conjunction with a study of FA represents a novel tumor-associated antigen.
This invention provides the isolation and characterization of a tumor associated antigen which can be used for immunodiagnosis, immunoprognosis, and therapy of human cancer. The antigen is a protein molecule with a molecular weight of about 35 kD. The antigen has been detected in serum of cancer patients.